Lenton Timothy M, van Oijen Marcel
Centre for Ecology and Hydrology, Edinburgh Research Station, Bush Estate, Penicuik, Midlothian EH26 0QB, UK.
Philos Trans R Soc Lond B Biol Sci. 2002 May 29;357(1421):683-95. doi: 10.1098/rstb.2001.1014.
We define the Gaia system of life and its environment on Earth, review the status of the Gaia theory, introduce potentially relevant concepts from complexity theory, then try to apply them to Gaia. We consider whether Gaia is a complex adaptive system (CAS) in terms of its behaviour and suggest that the system is self-organizing but does not reside in a critical state. Gaia has supported abundant life for most of the last 3.8 Gyr. Large perturbations have occasionally suppressed life but the system has always recovered without losing the capacity for large-scale free energy capture and recycling of essential elements. To illustrate how complexity theory can help us understand the emergence of planetary-scale order, we present a simple cellular automata (CA) model of the imaginary planet Daisyworld. This exhibits emergent self-regulation as a consequence of feedback coupling between life and its environment. Local spatial interaction, which was absent from the original model, can destabilize the system by generating bifurcation regimes. Variation and natural selection tend to remove this instability. With mutation in the model system, it exhibits self-organizing adaptive behaviour in its response to forcing. We close by suggesting how artificial life ('Alife') techniques may enable more comprehensive feasibility tests of Gaia.
我们定义了地球上盖亚生命系统及其环境，回顾了盖亚理论的现状，介绍了复杂性理论中可能相关的概念，然后尝试将它们应用于盖亚。我们从盖亚的行为角度考虑它是否是一个复杂适应系统（CAS），并认为该系统是自组织的，但并不处于临界状态。在过去38亿年的大部分时间里，盖亚一直支撑着丰富的生命。大型扰动偶尔会抑制生命，但系统总能恢复，且不会丧失大规模捕获自由能和循环利用基本元素的能力。为了说明复杂性理论如何帮助我们理解行星尺度秩序的出现，我们展示了一个虚构星球雏菊世界的简单细胞自动机（CA）模型。由于生命与其环境之间的反馈耦合，该模型呈现出涌现的自我调节。原始模型中不存在的局部空间相互作用，可通过产生分岔状态使系统不稳定。变异和自然选择倾向于消除这种不稳定性。在模型系统中引入突变后，它在对强迫的响应中表现出自组织适应性行为。最后，我们提出人工生命（“Alife”）技术如何能够对盖亚进行更全面的可行性测试。
